Cathode-ray tube



June 19, 1945. M, MEssNER ETAL 2,378,569!" CATHODE RAY TUBE Filed April 1,' 1941 yfree end.

throughfthe open end thereof. pressed into a ceramic disc T. A disc-shaped UNITED ISTATES PATENT OFFICE CATHODE-RAY TUBE Maximilian Messner and Erich Schantl, Berlin,

G dian ermany; vested in the Alienv Property Custo- Applica'tion April 1, 1941, Serial No. 386,266. In Germany March 29, 1940 3 Claims.

yIn cathode ray tubes or socalled Braun tubes the distance between the emissive layer and the control electrode should be the same at any ternperature, in order to render the characteristic controly line invariable in position. In many cases 1 the cathode is a metal cylinder in which a heating coil is arranged and which at its front end carries the emissive layer. This cylinder expands in accordance with the temperature the cathode acquires. The practice has been to fix the cylinder atthe end (remote from the emissive'layer. As a result, with rising temperaturethe cylinder yexpands toward the control electrode and thus brings the emissive layer nearer to this eleotrode. Therefore, it has been proposed to mount the cylinder by means of a device arranged to Withdraw from the controlr electrode whenever the't'emperature rises.` Such device, however, is

.complicated'and its operation does'not give th desired result, y

The present invention therefore -proposes that held in position with the aid of supporting means by which it is engaged at ,a zone located in close v,proximity to the emissive layer. In this way, the

i cylinder is prevented from expanding toward the control electrode. It will expand instead in the opposite direction, that is, in the direction of its The accompanying drawing is a fragmentary sectional View of a cathode ray tube as provided by the invention.

The emissive vlayer, E is tted to one end of a tubular metal cylinder Z, which is closed at this end While its other end is open. Fixed within this cylinder is a heating coil I-I,` inserted Cylinder Z 'is control electrode S is spaced from the layer E by a desired ldistance aiorded by an insulating ring R that rests against disc T or is formed integral therewith. The parts T, R, S may be held together by a, tubular body D of moulded insulating `material. In addition, a suitable clamping device, not shown for simplicity, may

` be used to press the parts T, R, S` together.

( Cl. Z50-162) vcathode arrangement H, Z to three sufficiently strong connectors V and thereby to pro-tect them from injury. The connectors V may be wires or tapes4 and are secured in the. stem of the bulb C in a well-known manner not represented here.

It will be seen that the arrangement Z, E', H,

f T, R, D, N1, N2, B may be added as a whole to the cathode cylinder, that is, ythe metal cylinder which at one end carries the emissive layer, be

the electrode system of a cathode ray tube, a guide G for the cathode structure ,being arranged in the bulb C. The cathode structure is hence exchangeable, and as it is a separate body, the act of arranging the cathode structure may be the last step in the manufacture of such a tube, namely, a step effected with the avoidance of an unduly high sealing temperature. y

What is claimed is:

1. A cathode ray tube having a, cathode structure that comprises a tubular metal cylinder, an

emissive layer tted to one end thereof, and insulating means to support this cylinder, such/supporting means being fitted to that end of the cyl- 'I'he disc T carrying the cylinder Z is'iitted to it at a zone adjacent to the emissive layer E. The cylinder thus `has a portion that projects from discT and on the side thereof remote :from layer `E. Thisfportion is free to expand during the inderwhichcarries the emissive layer while the remaining portion of the cylinder is free to expand, a vheating coil in said cylinder, a pair of rigid Vmetallic rods `fastened to said supporting means adjacent said cylinder but spaced therefrom, an insulating bridge member joining said rods and supported thereby, a conducting terminal mountet on said bridge member and spaced from said rods, and electrical connections from the cylinder and the ends of the heating coil to said rods and terminal respectively.

2. A cathode ray tube as recited in claim 1 including, a grid mounted on said supporting means in spaced relation with that end of the cylinder which carries the emissive layer.

3. A cathode ray tube as recitedin claim v1 in which said metallic rods are hollow, and aper- 

